In order to extract maximum information from electroretinographic waveforms obtained under clinical conditions, it is necessary to have reliable quantitative methods to characterize both the amplitude and shape of these waveforms. When sinusoidally modulated light is used to stimulate the retina, the resulting ERG potentials are, in general, not sinusoidal due to nonlinearities in the system. However, the responses are very reproducible and can easily be characterized by a few parameters based on a Fourier Analysis. The more conventional flash ERG, although usually of higher amplitude, is much less reproducible in shape and needs many more parameters to characterize completely. It is proposed to investigate thoroughly the human ERG to sinusoidal light stimulation, to establish precise relationships to stimulus parameters and other parameters of visual function in both normal and clinical patients. Specifically, the following variables will be considered: (1) Stimulus: modulation percentage, modulation frequency, color, average light level, and size of stimulated retinal area; (2) Disease and abnormal states of the retina: color blindness, night blindness, hereditary retinopathies, diabetic retinopathies, abnormal retinal circulation, etc. During the proposed project period we expect to obtain data covering a wide variety of retinal diseases (estimated 300 patients). These data will be on computer tape and available for any type of quantitative analysis. Our ultimate goal is to establish a firm quantitative basis for clinical electroretinography and to provide the clinician with additional data which can be useful in the diagnosis of retinal diseases.